Vitralis

Five panes wide, five shades of glass, and a panel marked 12×: which two glasses make twelve, and which of them still fits that column? Vitralis is a logic puzzle about restoring the stained glass of a cathedral at night. Every row and column holds each shade once, every lead-bound panel must make its number with its sign, and a panel lights in amber, ruby or blue the moment its glass is right. Each window has exactly one glazing, reached by reasoning alone. Beyond the Crossing the windows change. Grisaille panels hide their signs, so you work out whether they add, subtract, multiply or divide. Saltire windows cross the glass with two gold fillets, and both diagonals must hold every shade too. One window waits each evening at Vespers. When the last pane goes in, a beam of light crosses the window and spills its colours across the floor.